JUnit 4 compare Collections

Question

How would you succinctly assert the equality of collections elements, specifically a Set in JUnit 4?

Answer 1

with hamcrest:

assertThat(s1, is(s2));

with plain assert:

assertEquals(s1, s2);

NB:t the equals() method of the concrete set class is used

Answer 2

Check this article. One example from there:

@Test  
public void listEquality() {  
    List<Integer> expected = new ArrayList<Integer>();  
    expected.add(5);  

    List<Integer> actual = new ArrayList<Integer>();  
    actual.add(5);  

    assertEquals(expected, actual);  
}  

Answer 3

You can just assert that the two Sets are equal to one another, which invokes the Set equals() method.

public class SimpleTest {

    private Set<String> setA;
    private Set<String> setB;

    @Before
    public void setUp() {
        setA = new HashSet<String>();
        setA.add("Testing...");
        setB = new HashSet<String>();
        setB.add("Testing...");
    }

    @Test
    public void testEqualSets() {
        assertEquals( setA, setB );
    }
}

This test will pass if the two Sets are the same size and contain the same elements.

Answer 4

A particularly interesting case is when you compare

   java.util.Arrays$ArrayList<[[name,value,type], [name1,value1,type1]]> 

and

   java.util.Collections$UnmodifiableCollection<[[name,value,type], [name1,value1,type1]]>

So far, the only solution I see is to change both of them into sets

assertEquals(new HashSet<CustomAttribute>(customAttributes), new HashSet<CustomAttribute>(result.getCustomAttributes()));

Or I could compare them element by element.